The present invention relates to a position adjusting mechanism applicable as a mounting construction for a display device, for example, in a head mount display device, and a mounting device using the position adjusting mechanism.
A head mount display device has so far been used widely because an image can be seen easily with a wide screen, stereoscopic vision is easy, and the device can be moved together with an observer. Generally, such a head mount display device has a position adjusting mechanism for adjusting the position of display portion after the device is mounted.
FIG. 19 shows an example of a conventional head mount display device having a position adjusting mechanism. In FIG. 19, a display 100, which is the display portion, is attached to the distal end of a connecting member 112 extending from a front frame 110 constituting a head mount mechanism of the head mount display device via a support shaft 110a serving as a position adjusting mechanism. The support shaft 110a is attached so as to be rotatable against a predetermined frictional force (higher than the gravity of the display 100) with respect to the connecting member 112, and the display 100 fixed to the support shaft 110a is fixed to an arbitrary rotational position.
The head mount display device shown in FIG. 19 includes the front frame 110 which holds the display 100 as a mounting mechanism and is opposed to the front head of a wearer when the device is mounted, two side frames 101 which are attached at both ends, right and left, of the front frame 110 so as to be rotatable in the horizontal direction in a range of a predetermined angle and are opposed to the side heads of the wearer when the device is mounted, a flexible band 103 each end of which is attached to the side frame 101 so that the length thereof is adjustable, and a top frame 105 which connects the right and left side frames 101 to each other via flexible bands 106 attached so that the length thereof is adjustable and is opposed to the head top of the wearer when the device is mounted.
Also, a front pad 107 for pressing the front head of the wearer is provided on the inside in the center of the front frame 110, and a rear pad 104 for pressing the rear head of the wearer is provided on the inside in the center of the band 103.
Such a conventional head mount display device is mounted on a wearer as described below. First, knobs 102 provided on the right and left side frames 101 are moved in the direction indicated by the arrow A to adjust the length of the band 103, by which pressing forces against the front head and the rear head applied by the rear pad 104 and the front pad 107 of the head mount mechanism are adjusted. Next, knobs 108 provided on the top frame 105 is moved in the direction indicated by the arrow B to adjust the lengths of the bands 106, by which the top frame 105 is caused to abut on the head top of the wearer.
By the above-described operation, the front pad 107 provided on the front frame 110 and the rear pad 104 provided on the band 103 are pressed against the front head and the rear head of the wearer, respectively, by a fixed force, and the top frame 105 abuts on the top head, by which the display 100 connected to the front frame 110 is mounted on the head of the wearer.
Next, the wearer adjusts the optimum observation position by tilting the display 100 supported in front of eyes around the support shaft 110a. 
A problem with the conventional position adjusting mechanism consisting of a combination of the support shaft 110a and the connecting member 112 is that a range in which the display 100 is movable is limited to a range around the support shaft 110a, and although the angle is adjustable, the position in the vertical direction cannot be adjusted. For this reason, if the vertical position of the display 100 is incorrect when the device is mounted, the position cannot be adjusted to the optimum position even if the display 100 is tilted. Therefore, in the example shown in FIG. 19, the vertical position must be adjusted by moving the whole of the head mount display device vertically, so that it is necessary to perform the above-described mounting operation each time the vertical position is adjusted. This poses a problem in that the adjustment of position is very troublesome.
As a solution to this problem, Japanese Patent Laid-Open No. 9-280247 has disclosed a position adjusting mechanism in which the mounting construction of the connecting member 112 and the front frame 110 shown in FIG. 20 is improved to facilitate the adjustment of vertical position of the display 100.
This position adjusting mechanism consists of support shafts 110a and 110b and a connecting member 111 as shown in FIG. 20. In this position adjusting mechanism, the front frame 110 on the mounting mechanism side is connected to the connecting member 111 via the support shaft 110b, and the connecting member 111 can be rotated around the support shaft 110b with respect to the front frame 110. The support shaft 110b, like the support shaft 110a, is attached so as to be rotatable against a predetermined frictional force (higher than the gravity of the display 100) with respect to the connecting member 111. According to this mechanism, not only the display 100 can be tilted around the support shaft 110a but also the vertical position of the display 100 can be adjusted without repeating the mounting operation.
In FIG. 20, the support shaft 110a is taken as P1, the support shaft 110b as P2, the position of observer""s eye as I, and the line of sight of the observer as L1. Also, the foot of the perpendicular drawn from P1 to the line of sight L1 is taken as H, and IH is an observation distance a representing the positional relationship between the display 100 and the position of observer""s eye I. The observation distance a is a value determined in designing the head mount display device.
The position of P2 on the mounting mechanism side and the position of observer""s eye I depend on the shape and size of the head of an individual wearer and the condition in which the device is mounted, and is determined when the head mount display device is mounted on the head of the observer.
Therefore, when the observation distance a has an arbitrary value, the display device mounting position (support shaft) 110a (P1) is as described below.
First, since the length of P1H is a value inherent in the display device, if IH=a is determined, the length of IP1 connecting the eye I and the display mounting position 110a are determined unequivocally. Further, since the length of P1P2 is also a value inherent in the display device, P1 is an intersection of an arc having a radius of IP1 with I being the center and an arc having a radius of P1P2 with P2 being the center.
Therefore, in order to move the display 100 to the optimum observation position, it is necessary only that the display 100 be tilted around the support shaft 110a and the connecting member 111 is rotated around the support shaft 110b. 
In this case, however, the direction of the line of sight L1 is determined unequivocally, and cannot take an arbitrary value.
On the other hand, when the direction of the line of sight L1 is an arbitrary direction, the position of the display mounting portion 110a (P1) is determined as described below. If a straight line that is parallel with L1 and is at a distance of P1H is taken as L2, P1 lies on the straight line L2. Since the distance P1P2 takes a value inherent in the display device, P1 is an intersection of the straight line L2 and an arc having a radius of P1P2 with P2 being the center. In this case, however, the observation distance a cannot take an arbitrary value.
In order for both of the observation distance a and the direction of the line of sight L1 to be capable of taking an arbitrary value, the length of the connecting member 111 must be changed.
Specifically, P1 that meets a requirement that both of the observation distance a and the direction of the line of sight L1 be arbitrary is an intersection of an arc having a radius of IP1 with I being the center and the straight line L2 since the requirement is met when P1 lies on the straight line L2 and IH is equal to the observation distance a, P1. Therefore, it is necessary that the length of P1P2 do not take a constant value and be variable.
As described above, when the length of the connecting member 111 is fixed, the display 100 cannot meet the requirement that both of the observation distance a and the direction of the line of sight L1 be arbitrary. However, since the ordinary observation range has some degree of allowable range, the display 100 can be brought to the optimum observation position in the allowable range.
However, in order to move the display 100 to the optimum observation position by using the position adjusting mechanism shown in FIG. 20, it is necessary to rotate the connecting member 111 around the support shaft 110b while the display 100 is held by a hand and is tilted around the support shaft 110a. When this adjusting operation is performed, the display 100 can be tilted around the support shaft 110a by a rotational force only, but the support shaft 110b is subjected to a force in the direction indicated by the arrow A or B shown in FIG. 20 by a frictional force caused by friction. Specifically, a force in a direction such as to move the mounting mechanism vertically acts.
Generally, the mounting mechanism of this type has only a holding force of a degree necessary to hold the weight of device to reduce the burden on a wearer. Therefore, when the above-described force acts, the mounting mechanism itself moves undesirably, so that when the position of the display 100 is adjusted, the movement must be prevented, for example, by holding the mounting mechanism by a hand.
Japanese Utility Model Registration No. 3053061 has disclosed a position adjusting mechanism in which the friction of shafts corresponding to the support shafts 110a and 110b is adjusted with screws. Specifically, by loosening the screws, the shafts corresponding to the support shafts 110a and 110b are made capable of rotating freely with respect to the connecting member, and by tightening the screws, the shafts are finally fixed.
According to such a position adjusting mechanism, since the display and the connecting member are rotatable freely in the state in which the screws are loosened, a force is not applied to the mounting mechanism at the time of adjusting operation. When the display is fixed at the optimum position, however, an operation must be: performed in which screws provided on two shafts are tightened while the display and the connecting member are held by a hand in the freely rotatable state. Also, when the screws are loosened, the loosening operation must be performed while the display is held by a hand. Therefore, there arises a problem in that the operation is troublesome.
Also, in the above-described prior art, when the observer raises the display in an attempt to directly see the outside in the state in which the position has been adjusted, the friction of the support shaft cannot be released in the configuration of Japanese Patent Laid-Open No. 9-280247, so that the mounting mechanism may come off unless the mounting portion is held by a hand. Also, in the configuration of Japanese Utility Model Registration No. 3053061, the screws must be loosened, which poses a problem in that the operation for raising the display cannot be performed in a hurry.
The present invention has been made to solve the above problems with the prior art, and accordingly an object thereof is to provide a position adjusting mechanism attached between equipment the position of which is to be adjusted and a support portion the position of which is fixed, characterized in that an unnecessary force is not transmitted to the support portion when the position of the equipment is adjusted, and the adjustment of position can be made easily and surely.
Also, another object of the present invention is to provide a position adjusting mechanism attached between display equipment the position of which is to be adjusted and a support portion the position of which is fixed, characterized in that the position of the display equipment can be adjusted while a requirement that both of an observation distance and an observation direction be arbitrary at the same time is met.
Still another object of the present invention is to provide a position adjusting mechanism attached between display equipment the position of which is to be adjusted and a support portion the position of which is fixed, characterized in that the display equipment can be moved easily from the field of vision of an observer.
The gist of the present invention consists in a position adjusting mechanism which connects equipment the position of which is to be adjusted to support means for supporting the equipment so as to be movable relatively, comprising first movable means connected with the support means; second movable means connected with the equipment; first locking means moving between a first position at which the first movable means is locked and a second position at which the first movable means is movable; second locking means moving between a first position at which the second movable means is locked and a second position at which the second movable means is movable; and moving means for moving the first and second locking means at the same time, the moving means moving between a full locking position at which both of the first and second locking means move to the first position and a full unlocking position at which both of the first and second locking means move to the second position.
Also, another gist of the present invention consists in a head mount display device using the position adjusting mechanism in accordance with the present invention.